Jump to content

The RennTech.org community is Member supported!  Please consider an ANNUAL donation to help keep this site operating.
Click here to Donate

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Faults in the Vapor Recovery System

Recommended Posts

Hi Everyone:

I'm asking this for a local repairman who got stock on the Vapor Recovery System...

The car is a 2007 997 Carrera 4S with 60K KM on it.

The PIWIS faults are : P0456 "Evaporative emission system leak detected (very small leak) and P0455 "Evaporative emission system leak detected (large leak).

The mechanic has replaced the 1. gas vapor recovery tank, 2. the solenoid (I guess a valve on the engine's intake end), 3. gas cap, 4. the connecting hoses checked for leak. None of these steps corrected the faults. The faults were reset but would re-appear after couple of days driving.

He's clueless as to what else can go wrong. Help from anyone?



Link to comment
Share on other sites

hmmm, looks like he correctly tried to hit all the "possible causes" but unfortunately to no avail:


Leakage in fuel tank system

Diagnostic conditions

--Vehicle speed = 0 km/h

--Engine speed = 0 rpm

--Correction factor, height > 0.73

--Coolant temperature upon starting the engine may be no more than 6.8 K above ambient temperature

--Coolant temperature when engine starts > 3.8 °C

--Period for which the engine needs to have been running before ignition is switched off > 20 minutes

--Ignition has been switched off for at least 10 seconds.

--Ambient temperature 4 … 35.3 °C

--Active charcoal filter load < 3 for minor leak

--Fuel tank fuel level 10 … 54 litres

--Battery positive voltage 11.02 ... 14.5 V

--No fuel tank filling

--No faults detected for ambient pressure sensor, coolant temperature sensor, vehicle speed sensor

--No output stage faults detected for DMTL pump motor, DMTL switch-over valves and tank vent

--No fault detected for tank vent (flow)

The diagnostic conditions can also be established using the PIWIS Tester via the short test "tank leakage test". After the test has begun, the ignition must be switched off.


--In this context, please also observe the function description.

Possible fault causes

--Tank cap not closed correctly, leaking or missing

--Purge air line leaking

--Tank vent leaking

--DMTL (Tank Leakage Diagnostics Module) leaking

Link to comment
Share on other sites

  • Moderators

Thanks, Spiff, the only thing he's not done is replacing the gas tank itself... What is the "Tank vent leaking"? What to check on this item?

BTW, I know on older cars they'd by-pass the gas recovery system, but on 997, is it possible? If so, what's to look out for and how is it done?

The tank "vents" to the EVAP system, it is a closed loop arrangement that captures vapors and then burns them in the engine. Do a search, it is a common headache area for vacuum leaks. By-passing it is going to be a problem as the DME uses sensors to make sure it is functional, and they source of your codes. Disconnecting it is going to leave the car in permanent code conditon, so it may fail inspection (It is required for state and fed emissions regs in the US and many other countries).

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.